1. Field of the Invention
The present invention relates generally to an automotive engine coolant temperature determination method. More particularly, the present invention relates to a method using a cylinder head temperature sensor to infer such a temperature.
2. Disclosure Information
It is well known that malfunctions of engine cooling systems, such as a leak, will generally cause damage to the engine due to excessive engine overheating. To indicate such an event, a temperature sensing system for an internal combustion engine may include an engine coolant temperature (ECT) sensor, a cylinder head temperature (CHT) sensor, or a combination of the two. The temperature sensors record a temperature and relay the information to an electronic engine controller, which, in turn, relays the information to an operator, typically via an instrument display panel.
In ECT sensor equipped vehicles the sensor typically communicates with a coolant passage in a cylinder head. The problem with ECT sensor equipped vehicles is that an accurate reading of the CHT can not be obtained. Having an accurate CHT reading is important with respect to fuel economy and emissions.
In CHT sensor equipped vehicles the sensor typically communicates with the cylinder head at a location adjacent the combustion chamber of the engine. A problem with CHT sensor equipped vehicles is that the ECT can not be accurately calculated. For example, the CHT can be up to 70 degrees Fahrenheit hotter than the ECT and the temperature gauge would read hot when the system is really operating within a normal temperature range, thereby giving a "false reading".
To combat these problems many vehicles are equipped with both ECT and CHT sensors. A problem with a two sensor system is that it is more costly than the single sensor systems. A further problem is that the algorithm programmed into the engine controller is more complex because of the need to receive information from two sensors.
It would therefore be desirable to provide a method of accurately inferring ECT in CHT sensor equipped vehicles that overcomes the deficiencies associated with previous systems.